Ring-billed Gull

Leg color, size, and the bill. Ring-billed gulls are good sized gulls, but herring are even bigger! Then both of your birds were adults, so that helps with distinguishing bill characteristics, but immature birds don't have bills that look like that. And most gulls aren't adults until their 4th year haha

I have been known to make even the simplest things confusing!

1, 4, 6 = ring-billed gull 2, 3, 5 = herring gull

Ben is correct on the IDs, though the way the ID suggestion is done is rather confusing and not correct

Looks like 2 different birds. The one with yellow legs and a mostly yellow bill is a Ring-billed Gull. The larger one with pink legs and the yellow bill with a red spot is a Herring Gull.